![]() ![]() The effect is shown in the picture below. But even if you look at a model, this effect is very difficult to see and even more difficult to draw. Put more simply, in the long term the sacrum stops the 5 th lumbar vertebra from sliding forwards, the 5 th stops the 4 th, the 4 th stops the 3 rd, the 3 rd stops the 2 nd and the 2 nd stops the 1 st. The same lateral surfaces will prevent the upper vertebra from sliding forwards over the one beneath it. It is the effect that we are more concerned with here. The second effect is long term and involves stability. The lateral surfaces will come into contact with each other and prevent the spine from bending too far. The first is short-term and involves movement, the movement of bending your spine backwards (extension). On the sagittal plane of movement (backwards and forwards) the perfect articulation of the processes has two effects. This process continues up the lumbar spine through the 3 rd, 2 nd, and 1 st lumbar vertebra, where it changes slightly when the ribs come in contact with the spine. You will also see that the 5 th lumbar vertebra has upper (superior) articular processes that fit perfectly with the inferior articular processes of the 4 th lumbar vertebra above it. If you look at a full-size plastic model of the skeletal frame, you will see two wee lumps, called the superior articular processes, sticking out from the sacrum and fitting perfectly with the lower (inferior) articular processes of the 5 th and lowest lumbar vertebra. It is a function of the articular processes, and works like this. “ if the spine had all its ligaments and discs attached to it over its full length, and if the ligaments connecting it to the sacrum were also in place, then it would stand in the upright position.” There is another ingenious mechanism in the vertebral bones themselves that contributes to this. ![]()
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